Hydrastep 2468CB and 2468CD Manual | Introduction to the Hydrastep 2468 Electronic Gauging System |
1.1WATER LEVEL MEASUREMENT
The Hydrastep 2468 Electronic Gauging System is designed as an electronic alternative to water level gauges on boilers, giving a more reliable and safer water level indication than conventional visual gauges. It uses the significant difference in resistivities of water and steam in temperatures up to 370°C (698°F) to determine the water level.
Figure 1.2 - Schematic of resistance measuring cell and electrodes
A vertical row of electrodes is installed in the water level column attached to boiler and typically aligned so that half the electrodes are above and half below the normal water level (see Figure 1.2). The resistance measurement is made between the insulated tip of each electrode and the wall of the column.
The “cell constant” defining the actual resistance measured is determined by the length and diameter of the electrode tip and the column bore. In practice, the cell constant is chosen so that the resistance in water is less than 100k ohms and the steam resistance is greater than 10M ohms. Since the resistivities of water and steam are substantially different, the system is simple and requires no setting up adjustments. It is not susceptible to power supply variations, ambient temperature changes, etc., resulting in a highly reliable system.
A general overview showing how a typical Hydrastep 2468 System is installed is illustrated in Figure 1.3.
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